IEC 60118-13:2016

IEC 60118-13 ®
Edition 4.0 2016-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electroacoustics – Hearing aids –
Part 13: Electromagnetic compatibility (EMC)

Électroacoustique – Appareils de correction auditive –
Partie 13: Compatibilité électromagnétique (CEM)

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IEC 60118-13 ®
Edition 4.0 2016-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Electroacoustics – Hearing aids –

Part 13: Electromagnetic compatibility (EMC)

Électroacoustique – Appareils de correction auditive –

Partie 13: Compatibilité électromagnétique (CEM)

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 17.140.50; 33.100.20 ISBN 978-2-8322-3098-5

– 2 – IEC 60118-13:2016 © IEC 2016

CONTENTS
FOREWORD . 4

INTRODUCTION . 6

1 Scope . 7

2 Normative references . 7

3 Terms and definitions . 8

4 Operation and function of the hearing aid . 10

5 Specification of EMC environment . 10
6 Requirements for electromagnetic emissions . 10
6.1 Requirements for radiated emissions . 10
6.2 Limits of radiated emissions . 10
6.3 Procedure for radiated emissions . 10
7 Requirements for electromagnetic immunity . 10
7.1 General . 10
7.2 Compliance criteria . 10
7.3 Radiated RF electromagnetic fields . 11
7.3.1 General . 11
7.3.2 Requirements . 11
7.3.3 Procedure . 13
7.4 Electrostatic Discharge (ESD) . 13
7.4.1 Requirements . 13
7.4.2 Procedure . 13
7.5 Power frequency magnetic fields . 13
7.5.1 Requirements . 13
7.5.2 Procedure . 13
8 Test procedures for immunity to radiated RF electromagnetic fields . 13
8.1 General . 13
8.2 Test equipment and RF signal. 13
8.3 Hearing aid test setting . 13
8.4 Determination of gain . 14
8.5 Hearing aid output coupling during immunity test . 14
8.6 Position of the hearing aid during immunity test . 15

8.7 Measurement of the input related ambient noise (IRAN) . 17
8.8 Measurement of the output related interference level (ORIL) . 17
8.9 Calculation of the input related interference level (IRIL) . 18
8.10 Report . 18
9 Measurement uncertainty for immunity to radiated RF electromagnetic fields . 18
Annex A (informative) Background for establishing test methods, performance criteria
and test levels . 19
A.1 General . 19
A.2 Radiated RF electromagnetic fields, history of the test method . 19
A.3 Performance criteria . 21
A.4 Test field strengths – Bystander compatibility . 21
A.5 Field strengths – User compatibility . 21
Annex B (informative) Rationale for particular clauses and subclauses . 24
B.1 Rationale for Clause 6 Requirements for electromagnetic emissions . 24

B.2 Rationale for 6.1 Radiated emissions . 24

B.3 Rationale for Clause 6 Requirements for RF emissions and Clause 7

Requirements for electromagnetic immunity . 24

B.4 Rationale for 7.2 Compliance criteria . 24

B.5 Rationale for 7.3 Radiated RF electromagnetic fields . 24

B.6 Rationale for 7.4 Electrostatic discharge (ESD) . 24

B.7 Rationale for 7.5 Power frequency magnetic fields . 25

Bibliography . 26

Figure 1 – Examples of input-output response curves at 1 000 Hz and the
determination of gain at an input level of 55 dB . 14
Figure 2 – Example of a test arrangement for hearing aid immunity measurements
using a GTEM cell . 15
Figure 3 – Positioning of BTE, during RF exposure . 16
Figure 4 – Positioning of BTE with receiver, during RF exposure . 16
Figure 5 – Positioning of ITE with receiver, during RF exposure . 17
Figure A.1 – Ratio of 1:2 between field strength and interference level in dB . 20
Figure A.2 – Example of test arrangement for hearing aid immunity measurements
using dipole antenna . 22

Table 1 – Field strengths of RF test signals to be used to establish immunity for
bystander compatible and user compatible hearing aids . 12

– 4 – IEC 60118-13:2016 © IEC 2016

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
ELECTROACOUSTICS – HEARING AIDS –

Part 13: Electromagnetic compatibility (EMC)

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

International Standard IEC 60118-13 has been prepared by IEC technical committee 29:
Electroacoustics.
This fourth edition cancels and replaces the third edition published in 2011 and constitutes a
technical revision. This edition includes the following significant technical changes with
respect to the previous edition:
a) introduction of a new set of general EMC requirements for hearing aids.
It has the status of a product EMC standard in accordance with IEC Guide 107,
Electromagnetic compatibility – Guide to the drafting of electromagnetic compatibility
publications.
The text of this standard is based on the following documents:

FDIS Report on voting
29/889/FDIS 29/896/RVD
Full information on the voting for the approval of this standard can be found in the report on

voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 60118 series, published under the general title Electroacoustics –
Hearing aids can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 6 – IEC 60118-13:2016 © IEC 2016

INTRODUCTION
This international standard specifies EMC requirements of hearing aids. Most hearing aids

contain digital signal processors and some can contain wireless transceivers.

As the generic IEC 60601-1-2 EMC standard does not apply to hearing aids (ref.

IEC 60601-2-66:2015, 201.17), this revision of IEC 60118-13:2011 introduces additional

specifications for EMC requirements for hearing aids. Experience in connection with the use

of hearing aids in recent times has identified digital wireless devices such as wireless

telephones and GSM mobile phones as potential sources of disturbance for hearing aids.

Interference in hearing aids depends on the emitted power from the digital wireless device as

well as the immunity of the hearing aid. The performance criteria in this standard will not
totally ensure hearing aid user's interference and noise-free use of wireless telephones but
will establish useable conditions in most situations.
In practice, a hearing aid user, when using a wireless telephone, will seek, if possible, to find
a position on the ear that gives minimum or no interference in the hearing aid. Various test
methods have been considered for determining the immunity of hearing aids. When a digital
wireless device is used close to a hearing aid, there is an RF near-field illumination of the
hearing aid. However, validation investigations in preparing this standard have shown that it is
possible to establish a correlation between the measured far-field immunity level and the
immunity level experienced by an actual hearing aid used in conjunction with a digital wireless
device. The use of a far-field test has shown high reproducibility, and is considered sufficient
to verify and express the immunity of hearing aids. Near-field illumination of the hearing aid
(i.e. by generating an RF field using a dipole antenna) could however provide valuable
information during design and development of hearing aids.
In addition the standard now contains ESD radiated and immunity requirements to address
the EMC compliance, because manufacturers of hearing aids have faced questions of
compliance by agencies that require compliance to applicable standards. The lack of an
applicable standard can allow for misinterpretations and/or lack of agreement of applicable
standards. Without this revision other EMC standards may be applied which contain
requirements that are not relevant to hearing aids. This revision will now provide
manufacturers and test agencies a compliance standard that specifically addresses those
requirements.
Hearing aids are battery powered. Therefore, disturbances related to a.c. or d.c. power inputs
are not relevant and are identified as not applicable within this document. Hearing aids are
not normally connected to other equipment through cables, and therefore common mode
transients and common mode surges are not relevant and also identified as not applicable.
Hearing aids can now contain RF transceivers used for wireless communication, which comply

with existing standards addressed by entities such as the FCC, R&TTE or other wireless
directives. This revision is not intended to replace those standards but rather points the user
to those standards. National authorities on wireless and medical devices should be contacted
for advice. The users of this standard should consult the publications by those entities for
further knowledge to test communications of wireless hearing aids and use this standard to
supplement those needs.
It is recognized that the introduction of new wireless products coexists with existing spectra,
potential networks and other wireless products (medical as well as non-medical). This revision
does not address coexistence and the user of this standard should consult applicable entities
for guidance.
Hearing aids, where the outputs are non-acoustic, e.g. bone conduction hearing aids, are not
described directly in this standard, but the standard can be used if precise descriptions of
measurement setup for these types of hearing aids are given by the manufacturer.

ELECTROACOUSTICS – HEARING AIDS –

Part 13: Electromagnetic compatibility (EMC)

1 Scope
This part of IEC 60118 covers relevant EMC phenomena for hearing aids. Hearing aid

immunity to high frequency fields originating from digital wireless devices such as mobile
phones was originally identified as the most relevant EMC phenomena impacting hearing
aids. Since the inclusion of RF generating components within hearing aids, such as digital
signal processors or wireless transceivers, additional EMC compliance requirements apply.
The EMC requirements now included are radiated emissions and immunity to electrostatic
discharge, power frequency magnetic fields, and radiated RF electromagnetic fields.
Requirements associated with connected power and signal lines are not included.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and
are indispensable for its application. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60118-0, Electroacoustics – Hearing aids – Part 0: Measurement of the performance
characteristics of hearing aids
IEC 60118-7:2005, Electroacoustics – Hearing aids – Part 7: Measurement of the
performance characteristics of hearing aids for production, supply and delivery quality
assurance purposes
IEC 60118-15, Electroacoustics – Hearing aids – Part 15: Methods for characterising signal
processing in hearing aids with a speech-like signal
IEC 60318-5, Electroacoustics – Simulators of human head and ear – Part 5: 2 cm coupler
for the measurement of hearing aids and earphones coupled to the ear by means of ear
inserts
IEC 61000-4-2, Electromagnetic compatibility (EMC) – Part 4-2: Testing and measurement

techniques – Electrostatic discharge immunity test
IEC 61000-4-3, Electromagnetic compatibility (EMC) – Part 4-3: Testing and measurement
techniques – Radiated, radio-frequency, electromagnetic field immunity test
IEC 61000-4-8, Electromagnetic compatibility (EMC) – Part 4-8: Testing and measurement
techniques – Power frequency magnetic field immunity test
IEC 61000-4-20, Electromagnetic compatibility (EMC) – Part 4-20: Testing and measurement
techniques – Emission and immunity testing in transverse electromagnetic (TEM) waveguides
CISPR 11:2015, Industrial, scientific and medical equipment – Radio-frequency disturbance
characteristics – Limits and methods of measurement

– 8 – IEC 60118-13:2016 © IEC 2016

3 Terms and definitions
For the purposes of this document, the definitions given in IEC 60118-0, IEC 60118-7,

IEC 60118-15 and IEC 61000-4-3 as well as the following apply.

3.1
hearing aid
wearable instrument intended to aid a person with impaired hearing, usually consisting of a

microphone, amplifier, signal processor and earphone, powered by a low-voltage battery and

possibly also containing an induction pick-up coil and which is fitted using audiometric and

prescriptive methods
Note 1 to entry: Hearing aids can be placed on the body (BW), behind the ear (BTE), in the ear (ITE) or in the
canal (ITC).
3.2
bystander compatibility
immunity of a hearing aid that ensures it is usable in environments where digital wireless
devices are in operation in the proximity of the hearing aid wearer
3.3
user compatibility
immunity of hearing aid that ensures that it is usable when the wearer is using a digital
wireless device at the wearer's own aided ear
3.4
reference orientation
orientation of the hearing aid with respect to the RF emitting source which corresponds to the
orientation of the hearing aid under actual use on a person facing an RF emitting source
3.5
gain
G
difference between the acoustic or the magnetic equivalent input level (L ) and the respective
in
acoustic output level (L ).
p,out
Note 1 to entry: The gain is determined at an Acoustic Input Sound Pressure Level of 55 dB (SPL) or (for
induction pick-up coils) at a magnetic field strength level re 1 A/m of -35 dB which is the Magnetic Equivalent of
55 dB (SPL).
Note 2 to entry: G/dB= L / dB -55 .
p,out SPL
Note 3 to entry: If not stated otherwise in this document gain is determined at a frequency of 1 kHz.

3.6
output related interference level
ORIL
sound pressure level at the output of the hearing aid during exposure to a 1 kHz 80 %
amplitude modulated RF signal
Note 1 to entry: ORIL= L at 1 kHz, 80 % AM RF.
p,out
3.7
input related interference level
IRIL
ORIL with subtraction of gain:
IRIL= ORIL− G
Note 1 to entry: IRIL is used to characterize the immunity of the hearing aid.

3.8
input related ambient noise
IRAN
equivalent acoustic input sound pressure level that would lead to the acoustic noise output

produced by a hearing aid:
IRAN=-ORIL G
RF off
and
ORIL = L at (1 kHz, 80 % AM), RF switched off
RF off p,out
Note 1 to entry: IRAN is determined in the same way as IRIL but with the RF signal switched off.
3.9
GSM
global system for mobile communication
3.10
TEM cell
closed measuring device in which a voltage difference creates a TEM-mode electromagnetic
field
3.11
GTEM cell
TEM cell that has been altered to extend the usable frequency range
3.12
TDMA
time division multiple access
modulation technique used in digital wireless devices
3.13
code division multiple access
CDMA
modulation technique used in digital wireless devices
3.14
radio frequency
RF
frequency of electromagnetic radiation within the range of 30 kHz to 30 GHz
3.15
Input modes
3.15.1
microphone mode
hearing aid omnidirectional microphone active
3.15.2
induction pick-up coil mode
hearing aid induction pick-up coil active
3.15.3
directional mode
hearing aid directional microphones active

– 10 – IEC 60118-13:2016 © IEC 2016

4 Operation and function of the hearing aid

Hearing aids basically consist of a microphone, an amplifier, an optional induction pick-up coil

and a small earphone (receiver). For behind the ear (BTE) hearing aids the sound is often fed

to the ear canal by means of an individually made ear mould (ear insert), or with the receiver

in the auditory canal (RITE). In the ear (ITE) hearing aids have the active circuitry located in

the auditory canal.
The power source normally used is a small battery. On some hearing aids, the user can

perform some adjustments of the controls of the hearing aid.

5 Specification of EMC environment
Hearing aids are used in all environments as outlined in IEC 61000-4-3.
6 Requirements for electromagnetic emissions
6.1 Requirements for radiated emissions
Hearing aids shall comply with CISPR 11 requirements, based upon their classification.
Hearing aids are classified as group 1, class B equipment according to CISPR 11.
6.2 Limits of radiated emissions
Hearing aids shall comply with the limits of group 1, class B equipment as specified by
CISPR 11.
6.3 Procedure for radiated emissions
To ensure normal operating conditions the hearing aid´s wireless link shall be active (if
provided) and monitored. The hearing aid shall be exposed to an acoustic input. ISTS at
65 dB SPL ± 5 dB as defined in IEC 60118-15 should be used. The exclusion frequency band
(if needed) shall be documented in the test results.
The measurement can be carried out using a TEM waveguide in accordance with
IEC 61000-4-20.
7 Requirements for electromagnetic immunity

7.1 General
This clause specifies the EMC immunity requirements that are appropriate for hearing aids
covered by this standard. During all immunity tests the hearing instrument shall comply with
the immunity compliance criteria described in 7.2.
7.2 Compliance criteria
Under the immunity test conditions specified in Clause 8, the hearing aid shall be able to
provide basic safety and maintain performance. The following degradations, if associated with
basic safety, shall not be allowed:
• component failure;
• changes in programmable parameters;
• reset to factory defaults;
• change of operation mode;
• false alarms (battery and “loss of hearing aid at other side” alarms);

• errors in a calculated, stored or displayed numerical value sufficiently large to affect
diagnosis or treatment;
• output above the intended (programmed) maximum power output.

Loss of function during test is allowed, but the hearing aid shall return to normal state with no
loss of data (e.g. by switching instrument off and on again).

In addition during exposure to radiated RF electromagnetic fields:

• IRIL SPL shall not exceed 55 dB SPL.

7.3 Radiated RF electromagnetic fields
7.3.1 General
For the purpose of the radiated RF electromagnetic fields immunity test, two immunity classes
of hearing aids are defined (see 3.2 and 3.3) related to their use.
7.3.2 Requirements
Hearing aids shall comply with the criteria of 7.2 at immunity test levels as specified in
Table 1.
Table 1 states the field strengths of RF test signals to be used establish immunity for
bystander compatible and user compatible hearing aids. Bystander compatibility shall be
fulfilled as a minimum requirement, whereas user compatibility is an additional feature, which
can be claimed if the requirement is met by the hearing aid.
As sources of disturbance in the frequency range 0,96 GHz to 1,4 GHz below 0,7 GHz and
beyond 2,7 GHz are actually not known to affect hearing aids, testing for user compatibility in
these frequency ranges is not necessary, but may be considered in future. If the hearing aid
provides an additional microphone input mode – directional microphone – user compatibility is
not considered relevant in this position. Compatibility in induction pick-up coil mode is
considered important to establish interference free conditions in induction loop environments,
and to ensure the ability to use the induction pick-up coil as an input transducer for assistive
listening devices for digital wireless devices, e.g. portable hands free kits.

– 12 – IEC 60118-13:2016 © IEC 2016

Table 1 – Field strengths of RF test signals to be used to establish
immunity for bystander compatible and user compatible hearing aids
Bystander compatibility User compatibility
IRIL ≤ 55 dB SPL for field strengths, IRIL ≤ 55 dB SPL for field strengths,
E in V/m E in V/m
Frequency 0,08 to 0,7 0,7 to 96 0,96 to 1,4 1,4 to 2,0 2,0 to 2,7 2,7 to 6,0 0,08 to 0,7 0,7 to 0,96 0,96 to 1,4 1,4 to 2,0 2,0 to 2,7 2,7 to 6,0
range GHz
Microphone 3 3 3 3 3 Under Under 90 Under 50 35 Under
mode consideration consideration consideration consideration
Induction 3 3 3 3 3 Under Under 90 Under 50 35 Under
pick-up coil consideration consideration consideration consideration
a
mode
Directional 3 3 3 3 3 Under Under Under Under Under Under Under
microphone consideration consideration consideration consideration consideration consideration consideration
a
mode
Test field strengths are given as unmodulated carrier levels.
a
If provided by hearing aid.
NOTE In this fourth edition of IEC 60118-13, Table 1 has been updated for compliance to generic standards regarding bystander test levels. Additional national standards can
supplement ranges in Table 1.
7.3.3 Procedure
Test methods and equipment specified in Clause 8 apply.

The requirements to generate high field strengths might drive the RF power amplifier to

generate distortion. Care should be taken to ensure that distortion does not affect the

measurement results.
7.4 Electrostatic Discharge (ESD)

7.4.1 Requirements
Hearing aids shall be tested for immunity to electrostatic discharges. Hearing aids shall
comply with the criteria of 7.2 at immunity test levels of +2 kV, +4 kV, –2 kV and –4 kV for air
discharge and +8 kV and –8 kV for indirect contact discharge. The hearing aid shall be
discharged between every ESD exposure. Use of a carbon fiber brush or other mechanism to
remove the residual charge is allowed.
7.4.2 Procedure
Test methods and equipment for indirect contact discharge specified by IEC 61000-4-2 apply
(ungrounded table-top equipment).
7.5 Power frequency magnetic fields
7.5.1 Requirements
Hearing aids shall be tested for immunity to power frequency magnetic fields. Hearing aids
shall comply with the requirements of 7.2 at an immunity test level of 3 A/m for the
frequencies 50 Hz and 60 Hz.
In T-coil mode loss of function during test is allowed, but the hearing aid shall return to normal
state with no loss of data.
7.5.2 Procedure
Test methods and equipment specified by IEC 61000-4-8 apply (table-top equipment).
8 Test procedures for immunity to radiated RF electromagnetic fields
8.1 General
This clause describes the equipment and test methods for the radiated RF electromagnetic
field immunity test.
8.2 Test equipment and RF signal
Typical RF-test equipment, test configuration and test procedures as specified in
IEC 61000-4-20 shall be used.
8.3 Hearing aid test setting
The hearing aid gain control shall be adjusted to the reference test setting (RTS), and the
other controls shall be set to the basic settings as described in 7.3.3 in IEC 60118-7:2005
(‘adaptive features disabled’).

– 14 – IEC 60118-13:2016 © IEC 2016

8.4 Determination of gain
For the determination of gain use the same acoustic coupler and tubing (see 8.5) as used for

the ORIL measurement (see below) together with an anechoic chamber.

The gain of a hearing aid in microphone mode is determined by applying a sinusoidal 1 kHz

signal with a sound pressure level (L ) to be swept from (preferably) 30 dB to 80 dB at the
p,in
microphone reference point of the hearing aid, measuring the respective acoustic sound

pressure level (L ) at its output.
p,out
From this input-output response curve take the acoustic sound pressure level (L ) at 55 dB
p,out
input level. See examples in Figure 1.
For the gain of a hearing aid in directional mode use the gain obtained in microphone mode.
The gain of a hearing aid in induction pick-up coil mode is determined by applying a
sinusoidal 1 kHz signal with a magnetic field strength level (L ) re 1 A/m in dB to be swept
H,in
from -60 dB to –10 dB at the induction pick-up coil reference point of the hearing aid,
measuring the respective acoustic sound pressure level (L ) at its output.
p,out
From this input-output response curve take the acoustic sound pressure level (L ) re 1 A/m
p,out
at −35 dB input level (which is equivalent to the acoustic sound pressure level of 55 dB).
Calculate gain and inductive pick-up coil gain by:
G/dB= L / dB -55
p,out
130 120
120 110
110 100
Gain =
45 dB
Gain =
100 90
30 dB
90 80
50 60 70 80 90
50 60 70 80 90
Input SPL  (dB)
Input SPL  (dB)
IEC
Figure 1 – Examples of input-output response curves at 1 000 Hz
and the determination of gain at an input SPL of 55 dB
8.5 Hearing aid output coupling during immunity test
The hearing aid shall be placed in the RF field.
No objects other than the hearing aid, which could distort the RF-field, shall be present in the
test volume: In order to remove the metallic coupler as specified in IEC 60318-5 from the test
volume, the normal tubing between the hearing aid and the coupler shall be replaced by
tubing of 2 mm bore and with a length typically between 500 mm and 1 000 mm.
Output SPL  (dB)
Output SPL  (dB)
For in-the-ear instruments the outlet from the receiver shall be coupled to the tubing by a

suitable adapter. This adapter and the length of the tubing are not critical, as the hearing aid

gain is determined in each individual test configuration.

An example of a suitable test arrangement is given in Figure 2.

Hearing aids whose outputs are non-acoustic, e.g. bone conduction hearing aids will require

use of appropriate load and coupling device. Precise descriptions of measurement set-ups for

these types of hearing aids should be given by the manufacturer.

500 mm
∅2 mm tubing
Hearing aid
Directional coupler
GTEM cell
2cc coupler
RF signal
RF signal
Power amplifier Power sensor
Audio signal Mic. power supply
RF generator Power meter BP filter
1 kHz 1/3 Oct.
Measurement
instrument
Multimeter
interface
Measuring program
IEC
Figure 2 – Example of a test arrangement for hearing aid
immunity measurements using a GTEM cell

8.6 Position of the hearing aid during immunity test
The hearing aid shall be placed in the RF field in the reference orientation (see Figures 3, 4
and 5 and 3.4) and then be rotated in steps of 90° in the horizontal plane to measure ORIL at
the rotation angles of 0°, 90°, 180°, 270°.

– 16 – IEC 60118-13:2016 © IEC 2016

E
E
H
H
Field propagation
Field propagation
direction
direction
Rotation direction
16 mm
IEC
Figure 3 – Positioning of BTE, during RF exposure
E
E
H
H
Field propagation
Field propagation
direction
direction
X
X
Receiver
placement Receiver
placement
Rotation direction
16 mm
IEC
Figure 4 – Positioning of BTE with receiver, during RF exposure

E
E
H
H
Field
propagation Field propagation
direction
direction
Rotation direction
16 mm
IEC
Figure 5 – Positioning of ITE with receiver, during RF exposure
8.7 Measurement of the input related ambient noise (IRAN)
Perform an ORIL measurement with RF signal switched off to get ORIL
RF off.
Determine IRAN by subtracting gain (G) from ORIL : IRAN = ORIL –G.
RF off RF off
8.8 Measurement of the output related interference level (ORIL)
For each orientation (0, 90, 180, 270)° measure the sound pressure level (‘ORIL’) at the
output of the hearing aid:
– place the hearing aid in the respective orientation inside the test volume
– for each RF-frequency f = f *1,01 :
n+1 n
• apply the 1 kHz 80 % amplitude modulated RF signal with the field strength according
to Table 1,
• measure the sound pressure level (‘ORIL’) at the output of the hearing aid using a
1 kHz band-pass filter with a maximum bandwidth of one-third octave.
Measures should be taken to ensure that the background noise level of the test configuration
is at least 10 dB lower than the acoustic output (ORIL) from the hearing aid.
Gain changes in the hearing aid may occur due to RF carrier effects. This phenomenon can
be investigated by applying increasing field strength levels until hearing aid interference

occurs, and compare the increase in measured interference level to the increase in field
strength, or by applying a 1 300 Hz acoustic bias signal to the microphone input tube, which
sets the hearing aid to a known acoustic output level. With a frequency analyzer the hearing
aid acoustic output at 1 300 Hz can be measured to reveal gain changes in the hearing aid. If
gain changes are observed during the measurement it shall be stated in the test report, and
results should be interpreted with care as the RF carrier effects may have activated the signal
processing in the hearing aid in an unpredictable way.
Measurements for user compatibility and bystander compatibility can be carried out as two
separate tests according to Table 1. There is no need to perform a bystander compatibility
test if user compatibility is demonstrated. The measurements shall be carried out with the
microphone, directional microphone (if provided) and induction pick-up coil (if provided).
___________
1 % increment starting from the low side of the respective frequency range including the high side frequency.

– 18 – IEC 60118-13:2016 © IEC 2016

NOTE Rotation of the hearing aid in 4 discrete positions corresponding to the hearing aid placement under actual

use is found to be suitable for hearing aid immunity testing (see Annex A).

8.9 Calculation of the input related interferen
...